arXiv subjects

Masaki Yasue

Publications and source records attributed to Masaki Yasue.

At least 19 recordsLinked to original sources

arXiv2016

Excited Gauge and Higgs Bosons in the Unified Composite Model

In the unified subquark model of all fundamental particles and forces, the mass of the Higgs boson in the standard model of electroweak interactions ($m_H$) is predicted to be about $2\sqrt{6}m_W/3$ (where $m_W$ is the mass of the charged weak boson, $W$), which agrees well with the experimental values of about 125 GeV recently found by the ATLAS and CMS Collaborations at the LHC. It seems to indicate that the Higgs boson is a composite of the iso-doublet spinor subquark-antisubquark pairs well described by the unified subquark model with either one of subquark masses vanishing or being very small compared to the other. In the unified composite model, the masses of excited weak gauge bosons, $W^\ast$ and $Z^\ast$, and Higgs bosons, $H^\ast$, as well as excited quarks and leptons are all predicted to be of the order of the composite mass scales, say 1 TeV, and to satisfy the relation of $m_Wm_{W^\ast} = m_Zm_{Z^\ast}\cosθ_w$ (where $θ_w$ is the weak mixing angle). It strongly suggests that the excess of di-boson resonance events recently found by the ATLAS Collaboration at about 2 TeV may be explained by the productions and decays of the first excited states of either one of the weak and Higgs bosons, and the glueballs.

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arXiv2014

Parameterization of Pontecorvo-Maki-Nakagawa-Sakata mixing matrix based on CP-violating bipair neutrino mixing

CP violation in neutrino interactions is described by three phases contained in Pontecorvo-Maki-Nakagawa-Sakata mixing matrix ($U_{PMNS}$). We argue that the phenomenologocally consistent result of the Dirac CP violation can be obtained if $U_{PMNS}$ is constructed along bipair neutrino mixing scheme, namely, requiring that $ | U_{12} | = | U_{32} | {\rm and} | U_{22} | = | U_{23} | (\rm case 1)$ and $ | U_{12} | = | U_{22} | {\rm and} | U_{32} | = | U_{33}| (\rm case 2)$, where $U_{ij}$ stands for the $i$-$j$ matrix element of $U_{PMNS}$. As a results, the solar, atmospheric and reactor neutrino mixing angles $θ_{12}$, $θ_{23}$ and $θ_{13}$, respectively, are correlated to satisfy $\cos 2{θ_{12}} = \sin^2θ_{23} - \tan^2θ_{13}$ (case 1) or $\cos 2{θ_{12}} = \cos^2θ_{23} - \tan^2θ_{13}$ (case 2). Furthermore, if Dirac CP violation is observed to be maximal, $θ_{23}$ is determined by $θ_{13}$ to be: $\sin^2θ_{23} \approx ({\sqrt 2 - 1})({\cos^2θ_{13} + \sqrt 2 \sin^2θ_{13}})$ (case 1) or $\cos^2θ_{23} \approx ({\sqrt 2 - 1})({\cos^2θ_{13} + \sqrt 2 \sin^2θ_{13}})$ (case 2). For the case of non-maximal Dirac CP violation, we perform numerical computation to show relations between the CP-violating Dirac phase and the mixing angles.

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arXiv2014

Composite Higgs Boson in the Unified Subquark Model of All Fundamental Particles and Forces

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arXiv2014

CP violation in modified bipair neutrino mixing and leptogenesis

We study effects of CP violation in a modified bipair neutrino mixing scheme predicting $\sin^2θ_{23}$ near both 0.4 and 0.6 currently consistent with experimentally allowed values. The source of CP violation is supplied by charged lepton mixing accompanied by a single phase, whose mixing size is assumed to be less than that of the Wolfenstein parameter for the quark mixing. Including results of leptogenesis, which is based on the minimal seesaw model, we obtain the allowed region of CP-violating Dirac and Majorana phases, which provides the observed baryon asymmetry of the universe in the case of the Dirac neutrino mass matrix subject to one zero texture.

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arXiv2013

CP violation in bipair neutrino mixing

There are experimentally determined two best-fit points for the atmospheric neutrino mixing angle $θ_{23}$: $\sin^2 θ_{23} = 0.413$ (case A) and $\sin^2 θ_{23} = 0.594$ (case B). In the bipair neutrino mixing scheme, we predict $\sin^2θ_{23} = \sqrt{2}-1$ (case 1) to be consistent with the case A and $\sin^2θ_{23} = 2-\sqrt{2}$ (case 2) to be consistent with the case B. If the case B is realized in nature, the bipair neutrino mixing provides a unique neutrino model consistent with the observation $\sin^2 θ_{23} = 0.594$. However, the reactor neutrino mixing angle $θ_{13}$ is predicted to be $\sin^2θ_{13} = 0$, which is inconsistent with the observation. We propose a new modification scheme to yield $\sin^2θ_{13} \neq 0$ utilizing the charged lepton contribution and study its effect on both of CP-violating Dirac and Majorana phases, which is numerically estimated. It is found that there appear striking differences between the case 1 and the case 2 in their phase structure.

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arXiv2012

Generalized Scaling Ansatz and Minimal Seesaw Mechanism

Generalized scaling in flavor neutrino masses $M_{ij}$ ($i,j$=$e,μ,τ$) expressed in terms of $θ_{SC}$ and the atmospheric neutrino mixing angle $θ_{23}$ is defined by $M_{iτ}/M_{iμ}$ = $- κ_it_{23}$ ($i$=$e,μ,τ$) with $κ_e$=1, $κ_μ$=B/A and $κ_τ$=1/B, where $t_{23}=\tanθ_{23}$, $A$=${\cos ^2}{θ_{SC}}+{\sin ^2}{θ_{SC}}t_{23}^4$ and B=${\cos ^2}{θ_{SC}}-{\sin ^2}{θ_{SC}}t_{23}^2$. The generalized scaling ansatz predicts the vanishing reactor neutrino mixing angle $θ_{13}=0$. It is shown that the minimal seesaw mechanism naturally implements our scaling ansatz. There are textures satisfying the generalized scaling ansatz that yield vanishing baryon asymmetry of the Universe (BAU). Focusing on these textures, we discuss effects of $θ_{13}\neq 0$ to evaluate a CP-violating Dirac phase $δ$ and BAU and find that BAU is approximately controlled by the factor $\sin^2θ_{13}\sin(2δ-ϕ)$, where $ϕ$ stands for the CP-violating Majorana phase whose magnitude turns out to be at most 0.1.

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arXiv2012

Phases of Flavor Neutrino Masses and CP Violation

For flavor neutrino masses M^{PDG}_{ij} (i,j=e,mu,tau) compatible with the phase convention defined by Particle Data Group (PDG), if neutrino mixings are controlled by small corrections to those with sin(theta_{13})=0 denoted by sin(theta_{13})deltaM^{PDG}_{e tau} and sin(theta_{13})deltaM^{PDG}_{tau tau}, CP-violating Dirac phase delta{CP} is calculated by using these corrections. If possible neutrino mass hierarchies are taken into account, the main source of delta{CP} turns out to be deltaM_{e tau}^{PDG} except for the inverted mass hierarchy with {m}_1 approx -{m}_2, where {m}_i=m_ie^{-i varphi_i} (i=1,2) stands for a neutrino mass m_i accompanied by a Majorana phase varphi_i for varphi_{1,2,3} giving two CP-violating Majorana phases. We can further derive that delta_{CP} approx arg(M_{e mu}^{PDG})-arg(M_{mu mu}^{PDG}) with arg (M_{e mu}^{PDG}) approx arg(M_{e tau}^{PDG}) for the normal mass hierarchy and delta_{CP} approx arg(M_{ee}^{PDG})-arg(M_{e tau}^{PDG})+pi for the inverted mass hierarchy with {m}_1 approx {m}_2. For specific flavor neutrino masses M_{ij} whose phases arise from M_{e mu,e tau,tau tau}, these phases can be connected with arg(M_{ij}^{PDG}) (i,j=e,mu,tau). As a result, numerical analysis suggests that Dirac CP-violation becomes maximal as |arg(M_{e mu})| approaches to pi/2 for the inverted mass hierarchy with {m}_1 approx {m}_2 and for the degenerate mass pattern satisfying the inverted mass ordering and that Majorana CP-violation becomes maximal as |arg(M_{tau tau})| approaches to its maximal value around 0.5 for the normal mass hierarchy. Alternative CP-violation induced by three CP-violating Dirac phases is compared with the conventional one induced by delta{CP} and two CP-violating Majorana phases.

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arXiv2012

Generalized Scaling in Flavor Neutrino Masses

Scaling in flavor neutrino masses $M_{ij}$ ($i,j$=$e,μ,τ$) can be described by two angles: $θ_{SC}$ and the atmospheric neutrino mixing angle $θ_{23}$. For $A$=${\cos ^2}{θ_{SC}}+{\sin ^2}{θ_{SC}}t_{23}^4$ and B=${\cos ^2}{θ_{SC}}-{\sin ^2}{θ_{SC}}t_{23}^2$, where $t_{23}=\tanθ_{23}$, our scaling ansatz dictates that $M_{iτ}/M_{iμ}$ = $- κ_it_{23}$ ($i$=$e,μ,τ$) with $κ_e$=1, $κ_μ$=B/A and $κ_τ$=1/B and leads to the vanishing reactor neutrino mixing angle $θ_{13}=0$. This generalized scaling is naturally realized in seesaw textures. To obtain $θ_{13}\neq 0$ as required by the recent experimental results, we introduce breaking terms of scaling ansatz, which are taken to keep $M_{μτ}/M_{μμ}$ = $- κ_μt_{23}$ intact even at $θ_{13}\neq 0$. We derive relations that connect CP violating phases with phases of flavor neutrino masses, which are found to be numerically supported. The angle $θ_{SC}$ is observed to be $0.91 \lesssim\sin^2θ_{SC}\lesssim 0.93$ for the normal mass hierarchy and $\sin^2θ_{SC}\lesssim 0.33$ for the inverted mass hierarchy. Also observed is the size of $|M_{ee}|$ to be measured in neutrinoless double beta decay, which is 0.001-0.004 eV (0.02 eV-0.05 eV) in the normal (inverted) mass hierarchy.

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arXiv2012

Charged lepton contributions to bipair neutrino mixing

The bipair neutrino mixing describes the observed solar and atmospheric mixings; however, it predicts vanishing reactor mixing angle, which is inconsistent with the observed data. We explore the ways of minimally modifying the bipair neutrino mixing by including charged lepton contributions. There are two categories of the bipair neutrino mixing which are referred to as case 1 and case 2. It turns out that, without arbitrary phases, a minimal modification is realized by just considering one $e$ - $τ$ contribution from the charged lepton sector in the case 1. On the other hand, not only $e$ - $τ$ contribution but also $μ$ - $τ$ contribution is required to realize a minimal modification in the case 2.

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arXiv2011

Majorana CP phases in bi-pair neutrino mixing and leptogenesis

We estimate Majorana CP phases for a given flavor neutrino mass matrix (M_ν) consistent with the bi-pair neutrino mixing, which is recently proposed to describe neutrino mixings given by \sinθ_{13}=0 for the reactor neutrino mixing, \sin^2θ_{12} = 1-1/\sqrt{2} for the solar neutrino mixing and either \sin^2θ_{23} = \tan^2θ_{12} or \sin^2θ_{23}=1-\tan^2θ_{12} for the atmospheric neutrino mixing. Sizes of Majorana CP phases are evaluated so as to generate the observed baryon asymmetry in the universe via a leptogenesis scenario within the framework of the minimal seesaw model, where M_νsatisfies det(M_ν)=0 and one active Majorana CP phase (ϕ) is present. Assuming the normal mass hierarchy for light neutrinos and one zero texture for a 3X2 Dirac neutrino mass matrix, we find that ϕlies in the region of 0.69<|ϕ|<0.92 [rad], which is converted into allowed regions of α=arg(M_{eμ}) and β=arg(M_{eτ}), where M_{ij} (i,j=e,μ,τ) denote the i-j matrix element of M_ν. The phases αand βturn out to satisfy 0.31<|α|<0.40 [rad] and -1.25<β<-0.32 [rad]. The approximate numerical equality of |ϕ|\approx 2|α| is consistent with our theoretical estimation of ϕ=ϕ_2-ϕ_3 for ϕ_2=-(α+β) and ϕ_3\approx α-βvalid for the normal mass hierarchy. We also find the following scaling property: (M'^{μμ}-M'^{ee}/t^2_{12})/M'^{μτ}=M'^{μτ}/(M'^{ττ}-M'^{ee}/t^2_{12})=-M'^{eτ}/M'^{eμ} (t^2_{12}=\tan^2θ_{12}=\sqrt{2}-1), where M'^{ij} stands for M_{ij} evaluated on the basis of the Particle Data Group's phase convention.

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arXiv2011

Bi-pair Neutrino Mixing

A new type of neutrino mixing named bi-pair neutrino mixing is proposed to describe the current neutrino mixing pattern with a vanishing reactor mixing angle and is determined by a mixing matrix with two pairs of identical magnitudes of matrix elements. As a result, we predict \sin^2θ_{12}=1-1/\sqrt{2}(\approx 0.293) for the solar neutrino mixing and either \sin^2θ_{23}=\tan^2θ_{12} or \cos^2θ_{23}=\tan^2θ_{12} for the atmospheric neutrino mixing. We determine flavor structure of a mass matrix M, leading to diagonal masses of m_{1,2,3}, and find that |M_{μμ}-M_{ee}/t^2_{12}|:|M_{μτ}|:|M_{ττ}-M_{ee}/t^2_{12}|=t^2_{23}:|t_{23}|:1 for the normal mass hierarchy if m_1=0, where t_{ij}=\tanθ_{ij} (i,j=1,2,3) and M_{ij} (i,j=e,μ,τ) stand for flavor neutrino masses. For the inverted mass hierarchy, the bi-pair mixing scheme turns out to satisfy the strong scaling ansatz requiring that |M_{μμ}|:|M_{μτ}|:|M_{ττ}|=1:|t_{23}|:t^2_{23} if m_3=0.

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arXiv2010

Flavor Neutrino Masses giving sinθ_{13}=0

Among neutrino mixings, the reactor mixing angle, θ_{13}, is observed to be almost vanishing and is consistent with θ_{13}=0. We discuss how the condition of θ_{13}=0 constrains models of neutrino mixings and show that, for flavor neutrino masses given by M_{ij} (i,j=e,μ,τ), two conditions of M_{eτ}=-e^{2iγ}tan(θ_{23})M_{eμ} and M_{ττ}=e^{4iγ}M_{μμ}+e^{2iγ}[2/tan(2θ_{23})]M_{μτ} lead to θ_{13}=0, where θ_{23} is the atmospheric neutrino mixing angle and γis its associated phase. The rephasing invariance can select two phases provided by α=arg(M_{eμ}) and β=arg(M_{eτ}), giving γ=(β-α)/2.

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arXiv2010

Majorana CP Violation in Approximately μ-τSymmetric Models with det(M_ν)=0

We discuss effects of Majorana CP violation in a model-independent way for a given phase structure of flavor neutrino masses. To be more predictive, we confine ourselves to models with $\det(M_ν)=0$, where $M_ν$ is a flavor neutrino mass matrix, and to be consistent with observed results of the neutrino oscillation, the models are subject to an approximate $μ$-$τ$ symmetry. There are two categories of approximately $μ$-$τ$ symmetric models classified as (C1) yielding $\sin^22θ_{23} \approx 1$ and $\sin^2θ_{13} \ll 1$ and (C2) yielding $\sin^22θ_{23} \approx 1$ and $Δm_\odot^2/|Δm_{atm}^2|\ll 1$, where $θ_{23(13)}$ stands for the mixing of massive neutrinos $ν_2$ and $ν_3$ ($ν_1$ and $ν_3$) and $Δm_ \odot ^2$ ($Δm_{atm}^2$) stands for the mass squared difference for atmospheric (solar) neutrinos. The Majorana phase can be large for the normal mass hierarchy and for the inverted mass hierarchy with $m_1\approx -m_2$ only realized in (C1) while they are generically small for the inverted mass hierarchy with $m_1\approx m_2$ in both (C1) and (C2). These results do not depend on a specific choice of phases in $M_ν$ but hold true in any models with $\det(M_ν)=0$ because of the rephasing invariance.

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arXiv2008

Leptonic CP Violation Induced by Approximately mu-tau Symmetric Seesaw Mechanism

Assuming a minimal seesaw model with two heavy neutrinos (N), we examine effects of leptonic CP violation induced by approximate mu-tau symmetric interactions. As long as N is subject to the mu-tau symmetry, we can choose CP phases of Dirac mass terms without loss of generality in such a way that these phases arise from mu-tau symmetry breaking interactions. In the case that no phase is present in heavy neutrino mass terms, leptonic CP phases are controlled by two phases alpha and beta. The similar consideration is extended to N blind to the mu-tau symmetry. It is argued that N subject (blind) to the mu-tau symmetry necessarily describes the normal (inverted) mass hierarchy. We restrict ourselves to mu-tau symmetric textures giving the tri-bimaximal mixing and calculate flavor neutrino masses to estimate CP-violating Dirac and Majorana phases as well as neutrino mixing angles as functions of alpha and beta. Since alpha and beta are generated by mu-tau symmetry breaking interactions, CP-violating Majorana phase tends to be suppressed and is found to be at most O(0.1) radian. On the other hand, CP-violating Dirac phase tends to show a proportionality to alpha or to beta.

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arXiv2007

Correlation between Leptonic CP Violation and mu-tau Symmetry Breaking

Considering the $μ$-$τ$ symmetry, we discuss a direct linkage between phases of flavor neutrino masses and leptonic CP violation by determining three eigenvectors associated with ${\rm\bf M}=M^\dagger_νM_ν$ for a complex flavor neutrino mass matrix $M_ν$ in the flavor basis. Since the Dirac CP violation is absent in the $μ$-$τ$ symmetric limit, leptonic CP violation is sensitive to the $μ$-$τ$ symmetry breaking, whose effect can be evaluated by perturbation. It is found that the Dirac phase ($δ$) arises from the $μ$-$τ$ symmetry breaking part of ${\rm\bf M}_{eμ,eτ}$ and an additional phase ($ρ$) is associated with the $μ$-$τ$ symmetric part of ${\rm\bf M}_{eμ,eτ}$, where ${\rm\bf M}_{ij}$ stands for an $ij$ matrix element ($i,j$=$e,μ,τ$). The phase $ρ$ is redundant and can be removed but leaves its effect in the Dirac CP violation characterized by $\sin (δ+ ρ)$. The perturbative results suggest the exact formula of mixing parameters including that of $δ$ and $ρ$, which turns out to be free from the effects of the redundant phases. As a result, it is generally shown that the maximal atmospheric neutrino mixing necessarily accompanies either $\sinθ_{13}=0$ or $\cos(δ+ρ)=0$, the latter of which indicates maximal CP violation, where $θ_{13}$ is the $ν_e$-$ν_τ$ mixing angle.

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arXiv2006

Two Categories of Approximately mu-tau Symmetric Neutrino Mass Textures

Our approximately μ-τsymmetric neutrino mass textures fall into two different categories, whose behaviors in the μ-τsymmetric limit are characterized by either \sin(theta_{13})->0 (referred to as C1)), or \sin(theta_{12})->0 (referred to as C2)). We present ten phenomenologically viable neutrino mass textures: two for the normal mass hierarchy, three for the inverted mass hierarchy, and five for the quasi degenerate mass pattern. Tiny μ-τsymmetry breaking ensures that \sin^2(theta_{13}) << 1 for C1), and Δm^2_\odot/Δm^2_{atm} (\equiv R) << 1 for C2). A correlation among small quantities is provided by \cos 2(theta_{23}) \sim \sin(theta_{13}) for C1), and by either \cos(2theta_{23}) \sim R, or \cos(2theta_{23})\sin(theta_{13}) \sim R for C2). It is further shown that \tan(2theta_{12}) \sim \cos(2theta_{23})/\sin(theta_{13}) is satisfied for C2). We find specific properties for each mass ordering, which are discussed in this article.

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arXiv2006

What Does mu-tau Symmetry Imply about Neutrino Mixings?

The requirement of the mu-tau symmetry in the neutrino sector that yields the maximal atmospheric neutrino mixing is shown to yield either sin(θ_{13})=0 (referred to as C1)) or sin(θ_{12})=0 (referred to as C2)), where θ_{12(13)} stands for the solar (reactor) neutrino mixing angle. We study general properties possessed by approximately mu-tau symmetric textures. It is argued that the tiny mu-tau symmetry breaking generally leads to cos(2θ_{23}) \simsin(θ_{13}) for C1) and cos(2θ_{23}) \sim Δm^2_\odot/Δm^2_{atm}(\equiv R) for C2), which indicates that the smallness of cos(2θ_{23}) is a good measure of the mu-tau symmetry breaking, where Δm^2_{atm} (Δm^2_\odot) stands for the square mass differences of atmospheric (solar) neutrinos. We further find that the relation R \sim sin^2(θ_{13}) arises from contributions of O(sin^2(θ_{13})) in the estimation of the neutrino masses (m_{1,2,3}) for C1), and that possible forms of textures are strongly restricted to realize sin^2(2θ_{12})=O(1) for C2). To satisfy R \sim sin^2(θ_{13}) for C1), neutrinos exhibit the inverted mass hierarchy, or the quasi degenerate mass pattern with | m_{1,2,3}| \sim O(\sqrt{Δm^2_{atm}}), and, to realize sin^2(2θ_{12})=O(1) for C2), there should be an additional small parameter ηwhose size is comparable to that of the mu-tau symmetry breaking parameter ε, giving tan(2θ_{12}) \sim ε/ηwith η\sim εto be compatible with the observed large mixing.

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arXiv2005

A New Type of Complex Neutrino Mass Texture and mu-tau Symmetry

Relying upon the usefulness of the μ-τsymmetry, we find a new type of neutrino mass texture with a single phase parameter δthat describes maximal atmospheric neutrino mixing and Dirac CP violation due to the presence of δ. The Majorana phase associated with the third massive neutrino turns out to be identical to the Dirac phase while other Majorana phases vanish. The nonvanishing reactor neutrino mixing angle θ_{13} is induced by a μ-τsymmetry breaking effect. Flavor neutrino masses that supply the μ-τsymmetry breaking terms become pure imaginary for δ=\pm π/2, leading to maximal CP violation. There is a parameter denoted by η, which is either O(\sqrt{Δm^2_\odot/Δm^2_{atm}}) in the normal mass hierarchy, or O(Δm^2_\odot/Δm^2_{atm}) in the inverted mass hierarchy. In the inverted mass hierarchy, the contribution of O(\sin^2θ_{13}) is found to be significant and cannot be neglected. Our texture also leads to quasi degenerate neutrinos with masses of O(\sqrt{Δm^2_{atm}}), which serves as the scale for the effective neutrino mass in (ββ)_{0ν}-decay. This texture does not include η, and Δm^2_\odot naturally arises from contributions of O(\sin^2θ_{13}) to give Δm^2_\odot/Δm^2_{atm}\sim\sin^2θ_{13}, yielding the prediction of \sin^2θ_{13}=O(10^{-2}).

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